"Voice" is not just a matter of text - of how you write.  It is also to do with the layout.  If you want to get an idea of "voice" in terms of design, take a look at a children's TV show on a saturday morning in which young looking people present a variety of events and films to children.   Then compare that with an after 9pm programme.  It is not just the content and language that is different - it is the entire tone of each piece - from the backdrop behind the people to the camera angles.

However just as your voice must, one way or another, use the English language when communicating with those who speak English, so no matter which approach to design you take, your design should start from certain key principles, known as the fundamentals of the psychology of perception.  

For more information of the way the psychology of perception underpins all successful design work read one or two of the articles on our Theory site on what works in direct mail.  You may find the articles on the following topics particularly helpful:

	Colour
	Commitment
	Elaboration likelihood
	Focus Zone
	Grabby Image